Doping dependence of the anomalous Hall effect in La1-x Srx Co O3

The anomalous Hall effect has been studied for single crystals of La1-x Srx Co O3 (0.17≤x≤0.30). The Hall conductivity for x=0.3 is proportional to the magnetization, which is consistent with the Kaplus-Luttinger theory. At the lowest temperature, it shows the highest reported value among transition-metal oxides (165 Ω-1 cm-1). For the lower doping crystals, by contrast, the Hall conductivity shows a downturn with decreasing temperature, being distinct from the temperature dependence of the magnetization. In particular, the Hall conductivity for x=0.17 shows a sign change around 50 K. The negative component of the Hall resistivity seems to be related to the glassy nature of the magnetism in this doping region.